Kubica will return as soon as he's fit - Boullier

German Heidfeld was drafted in to substitute for team regular Robert Kubica, who is recovering from serious injuries sustained in a February rally crash.

But it has been rumoured that relations between Enstone based Renault and Kubica's management is not all rosy, particularly after team figures and manager Daniele Morelli recently disagreed about the progress of the Pole's recovery.

German website motorsport-total.com quotes team boss Boullier as revealing at Silverstone that Kubica is "full of energy" after his latest surgery.

"I've spoken with Daniele and (Dr) Ricardo (Ceccarelli)," added the Frenchman. "It is more positive than expected."

Asked about Morelli's recent claim that Kubica might be fit to return at Interlagos in late November, he answered: "I hope that's true, but I'm not a clairvoyant."

Boullier did however scotch the suggestion that Renault will definitely race with Heidfeld alongside Petrov for the rest of the current season.

"We have a very clear agreement -- when Robert is fit enough to return, he will return at that point."